This invention relates to an exponential operation device which carries out an exponential operation of x.sup.y or x.sup.1/y related to a negative number x and can provide an answer. A compact electronic calculator for counting functions can generally carry out an exponential operation of x.sup.y or x.sup.1/y related to data x and data y. Where the data x represents a negative value, and answer sometimes takes an imaginary form. In such case, an answer derived from the exponential operation of x.sup.y has hitherto been treated as an error. Where, in the exponential operation of x.sup.y, data y denotes an integer, though data x represents a negative value, then an answer takes a real form. Where, in the exponential operation of x.sup.1/y, data y denotes an odd number, then an odd root of negative x includes at least one real root. Although a real root is present, an answer sometimes takes an imaginary form as described above. Since it is impossible to obtain a uniformly fixed answer, the conventional exponential operation device has the drawback of unavoidably treating an answer derived from the exponential operation of x.sup.y as an error.
It is an object of this invention to provide an exponential operation device which the above-mentioned drawbacks accompanying the prior art exponential operation device, and can determine a real answer in exponentially operating x.sup.y when y is an integer and x is a negative number and also in exponentially operating x.sup.1/y when data y represents an odd number.